Expanding brake



EXPANDING BRAKE Filed April 1l, 1927 2 Sheets-Sheet l Inveyzof: @4a/5%' A. H. G. Gamm@ EXPANDING BRAKE Filed April ll, 1927 2 Sheets-Sheet 2 ire no Walented [libert l'rlenry Godfrey Girling, llondon, England, assigner to Bendix Brake l)ornpanyy South Bend, llnd.

Application lllpril lll, 1927, Serial No. lZll'l, and in Great Britain Alpril ld, i926 dll Claims.

This invention relates to expanding brakes Yof the type wherein two brake-levers associated each with a brake-shoe, are arranged to be moved apart by an expanding member so as to force the shoes against a rotary member, such .itil

as a drum, to be braked.

Any rigid brake-shoe expanded into a rotating cylindrical brake-drum will tend, providing it abuts at its forward end against a fixed stop, to move outwards under the frictional drag of the drum, thereby adding to the pressure between the shoe and the drum; an important object of this invention is to utilize this selfenergizing action in an expanding brakegof the type described.

Another object is to render this self-energizing action as powerful as possible by providing either a long arc of contact of one shoe with the drum, or by making cumulative the selfenergizing action of two or more shorter shoes.

l. further object is to ensure that the pressure exerted on the bralradrum shall. be distributed as evenly as possible, and a still further object is to provide an expanding brake of the type de scribed which shall be more powerful than those used heretofore.

`iL/et another object is to provide a brake-lever and a shoe or shoes associated therewith which can be readily applied to existing brakes of the type described for converting them into the improved brale according to the invention.

According to an important feature of the vention, there is provided in an expanding brake of the character described7 the combination with a lever mounted to rock towards and away from a member to be bralred, and means for rocking the lever, of a hrake-shoe so movably supported on said lever that it is movable bodily on said lever in the direction of its length, and also when one end of the shoe moves away from its supn porting lever and towards the member to be braked, the other end of the shoe can move towards its supporting lever and away from the member to be braked, and a stop or stops for limiting the endwise movement of the shoe. Such a brake will be self-energizing owing to the trailing end of the shoe tending to move outwards against 'the drum under the action of the frictional drag of the latter.

According to another feature of the invention, two or more shoes arranged in successive relationship are associated in a similar manner with a single brake-lever, whichk shoes can be ex panded by a substantially radial force acting at or near the centre of each shoe.

(Cl. Hi8-'litt Conveniently, when two or more shoes are associated with a single lever, the shoes so cooperate one with another as to cause them to rock in unison, and also to cause the endwise movement of one shoe to be transmitted to a shoe situated in front thereof in the direction of rotation of the drum.

ln order to increase the self-energizing effect, according to another feature of the invention, the point of abutment of each shoe with. its stop preferably lies at a shorter radial distance from the axis of the drum than the length of the radius of the drum.

In this improved construction of brake, the

circumferential movement of the shoes `is not i arrested by the expanding device which may of any convenient construction for rocking the levers carrying the shoes.

The invention consists in the construction, arrangement and combination of parts described hereinafter and pointed out in the claims.

Several embodiments of the invention are diam grammatically illustrated by way of example in the accompanying drawings, wherein:-

Figure l is a side elevation showing an expanding braise of the type described according to the invention, the rotating member to be braked being omitted and the two lower shoes on the lower bralredever being shown in longitudinal section;

Figure 2 is a horizontal section taken on the line 2 2 in Figure l and showing the member to be braked in broken lines;

Figure 3 is a cross-section taken on the line 3-3 in Figure l, and

Figure Al is a cross-section taken on the line l-Ll of Figure l;

Figure 5 is a side elevation of a modified con-- struction of bralre according to the invention, one shoe being shown in section and the member to be braked being omitted;

Figure 6 is a section taken on the line 6--6 in Figure 5, the member to he bralred being shown in broken lines, and

Figure '7 is a vertical section taken on the line 7-7 in Figure 5; and

Figure d is a side elevation, partly in section through two shoes on one brake-lever, showing another modiiied construction of brake according to the invention.

Like reference numerals designate corresponding parts throughout the several views.

Referring to Figures l to d, four shoes lil, l1, l2 and 13 having attached frictional faces are supported in pairs on brakedevers 15 and 15 each by a single anti-friction roller whereof only two till designated 16 and 17 are shown, in such a way as to be free to rock and also to travel circumterentially in the direction of length of the levers. The shoes are held seated on the rollers, each of which constitutes a fulcrum-piece, by springs 18, 19, one for each pair of shoes, which springs prevent looseness and consequent rattling. These springs are anchored at the middle to the levers 14, l by fasteners in the form of U- shaped stirrups 20 and 21, and bear at their ends on spring clips 22, 23. These clips are attached at one end to the shoes and have their other ends lying each between the ends o the associated anti-friction roller, and hold the shoes seated in recesses provided for them in the associated brake-lever whereby rattling is avoided.

The levers lll, 15 rock about a pivot 24; which is preferably common to them both and is mounted in a housing formed on a stationary annular back plate or frame member 26. These levers can be expanded by a cam 27 which is formed or provided on a journal 28 of an operating lever 29 that is mounted in a housing 30 on the annular member 26 diametrically opposite the housing 25. Springs 31 and 32 attached to lugs on the levers 14, 15 bring all the parts back to their initial position after use.

The two shoes of each pair are compelled to rock in unison owing to their adjacent ends nexibly interlocking one with another as shown in Figures 1 and 4r. The shoes are of channel section, and at their adjacent ends one side of one shoe extends under the same side of the adjacent shoe, whilst at the opposite side of the shoes the arrangement is the reverse, so that when either shoe rocks in either direction it tends to rock the other shoe with it in the same direction. Also, the end of each shoe can bear against its adjacent shoe to cause the endwise movement of one shoe to be transmitted to the other. The opposite ends of each pair of shoes can abut against the housings 25, which constitute fixed abutment means or stops for limiting the endwise-movement of the shoes on their anti-friction rollers due to the tangential drag on them of the rotating member that is being braked. This member is indicated as a drum 35.

Assuming that the drum 35 is rotating clockwise as viewed in Figure 1 and the brake is being applied by rocking the operating lever 29, the brake-levers 14, 15 will exert an approximately radially-directed eiort at about the centre of each shoe through the anti-friction rollers. Owing to the tangential drag of the drum on the shoes the leading shoes 10 and 12 respectively of the two pairs will be arrested by abutting against the stops 30 and 25, respectively, whilst the trailing shoes 13 and 11 will move endwise on their rollers and abut endwise against the leading shoes 10 and 12, respectively, of the same pair. When the leading end of the shoe 10 abuts against the stop 30 its trailing end tends to move outwards under the frictional drag of the drum. At the same time the trailing end of the shoe 11 abuts against the adjacent end of the shoe 10 and the trailing end of the shoe 11 tends to rock about its fulcrum and move outwards. Owing to the two shoes 10, 11 being flexibly interlocked as described above the turning moments acting on the shoes tending to rock them about their points of support are largely counterbalanced and the pressure of the shoes on the brake-drum is evenly distributed.

It will be observed that eachshoe is recessed at its ends to abut against its co-operating stop 25 Leanser or 30 at a point situated at a radial distance from the center of rotation of the drum less than the radius of the internal periphery of the drum. Owing to this arrangement the tendency of the trailing ends of the leading shoes to move outwards is increased as compared with what it would be if the stop arresting the endwise movement of the shoe were placed at a greater distance from the centre of the drum.

As compared with an expanding brake of the type described of the construction usual heretofore wherein the shoes are xed on the brakelevers, the improved construction has the following advantages- (1) A largely increased eiective area of braking is obtained which may be as much as twice that provided heretofore. It will be noted that the shoes extend through a total arc of very nearvly 360.

(2) The balanced pressure on each shoe and the approximately 360 total arc of contact ensure very evenly distributed pressures on the brake-drum and absence of brake distortion.

(3) lEach shoe is definitely self-energizing, so that the brake power is increased.

(il) The brake is equally eiective in either direction of working.

(5) Since the radial expansive forces are developed at an angular distance of about from the expanding device and pivot of the levers, respectively, instead of as in the usual construction oi brake of the type described, the internal leverage ratio of the system is about 40% greater than the ratio of t-he said usual construction; this increases the power of the brake, and the total increase in braking power due to the self-energizing effect and the increased leverage ratio is more than (6) Slight additional increases in power result from there being smaller frictional losses in the expanding device;.in a customary brake oi the type described known heretofore half the braking tangential force is transmitted through the bearings of the expanding device to the fixed member of the brake. In the improved construction of brake according to the invention, this tangential force is transmitted directly to the fixed member, and as the forces acting on the expanding device are substantially balanced there is very little pressure on its bearings and little frictional loss. Both the expanding device and the pivot of the levers can consequently be made lighter than usual because they are not subjected to the braking torque.

(7) Owing to the described method of expand- 1 ing and supporting the four shoes they all move towards the drum at an equal rate, and recede through an equal distance, ensuring equal wear on all the shoes and an equal-clearance between the drum and each shoe when out of use. The shoes are pulled away from the drum positively and 'cannot touch or rub against the drum at their centres when out of use, these being the only points where the clearance is rigid; if the shoes touch at their ends it is easyfor the drum to displace them and so avoid heavy frictional contact.

(8) Since the clearance between the shoes and drum at points 90 apart is greater in the improved construction than at points a apart in the usual construction of brake of the type described, the points at which the clearance is rigid in the improved construction of brake, i. e. 90 apart, admit of a greater rigid clearance than in A Cn Leanser the usual construction 'with its 120 length of lining.

Referring now to Figures 5, 6 and 7, the brakelevers 14, 15 are separately pivoted at 41, 42, respectively, on a back plate 43 and carry each only one shoe 44, 45, respectively, movable circumferentially between stops 46, 47 provided diametrically opposite one another on the back plate 43 and extending at right-angles to the general plane of the latter. Journaled on each lever at or towards the middle of its length is a rotatable fulcrum-piece in the form of an antifriction roller 48, whereof the ends are of larger angular diameter than the middle portion which is seated in a semi-cylindrical bearing in the lever. Each shoe is of channel section and is mounted to rock on the enlarged ends of its associated roller 48 and can also move circumferentially between the fixed stops 46, 47. A steel spring 49 is secured as by rivets to each shoe near the middle thereof and has its ends deflected to bear under the stops 46, 47, and thereby tends to hold the shoe seated on its roller. A middle portion of the spring is interposed between the shoe and its roller, as clearly shown in Figure 6, and forms a wear-resisting bearing for the shoe.

When the brake is to be applied the expanding device 27 is actuated by the arm 29 and the brake operates in either direction substantially as described above with reference to Figures 1 to 4. In this construction each shoe subtends a greater angle, namely about 135, than that subtended by a single shoe in the construction shown in Figure l, and the point of contact of either end of a shoe with its fixed stop is situated further from the centre of the drum than in the construction shown in Figure l.

The construction of brake shown in Figure 8 is similar to that shown in Figure 5, but differs therefrom in that two shoes 50 are associated with each brake-lever and a xed stop 51 corresponding to the stops 46, 47 in Figure 5, is provided between each two adjacent shoes. These stops have a shorter angular length than the stops 46, 47 and serve as abutments for the shoes 50 .and for the springs 49. The operation of` this modified construction will be readily understood from the above.

When the pivots of the levers 14, 15 and the expanding device, such as 27, are arranged vertically one above the other as shown in Figure 5, the shoes of this brake can move bodily in a vertical direction through a small distance, so that if the axis of the road wheel axle and the axis of the axle fail to coincide either momentarily owing to shock, or permanently owing to distortionor wear of the parts,l the shoes can accommodate themselves to the altered position of the drum and thereby avoid the sudden increases in braking resistance due to such distortion or displacement of the relative positions of the rotating and of the stationary parts of the brake assembly. In some cases it may be desirable to make the lower stop 47 in Figure 5 and the lowest stop 51 in Figure 8 rather thicker than the upper stop, as shown in Figure 8. This would permit the deflection of the springs 49 to be increased at their lower ends in such a way as to counteract the radial force developed at the lowed ends of the shoes resulting from the reaction of the Weight of the shoes upon the abutting surface of the stop. It will be observed that in both of the constructions shown in Figures 5 and 8 the plane containing the axes of the lever pivots and of the associated expanding device passes not through the middle of the adjacent stops, but to one side thereof, the brake-shoes, their anti-friction rollers and the stops for limiting the endwise movement of the shoes being displaced angularly about the centre of the brake-drum from a position in which they would lie symmetrically at the two sides of the said plane.

Various modifications may be made in the details of construction described above without departing from the scope of the invention as defined in the claims. For example, the fulcrumpieces for the shoes may be situated nearer one end of the shoe than the other, particularly if the barke is intended to be used principally with a member that normally rotates in one directio only. 1

I claim:

l. In an expanding brake, the combination with a brake-lever, of a brake-shoe adapted to rock about an axis lying transversely of the lever and movable on said lever in the direction of its length and diametrically disposed fixed stops for arresting the endwise movement of the shoe.

2. In an expanding brake of the character described, the combination with a brake-lever, of brake-shoes so mounted in successive relationship thereon as each to be able to rock about an axis lying transversely of the lever and also to be movable on said lever in the direction of its length and a iixed stop for arresting the endwise movement of the brake-shoes.

3. In an expanding brake of the character described, the combination with a brake-lever, of a fulcrum-piece rotatably mounted thereon, a brake-shoe mounted to rock on said fulcrumpiece about an axis lying transversely of the length of the lever, which shoe is also movable endwise on the fulcrum-piece in the direction of length of the lever, and a spring tending to hold said shoe seated on said fulcrum-piece,y a part of which spring is interposed between the shoe and the fulcrum-piece and serves as a bearing for the shoe. f

4. Inan expanding brake, the combination with a brake-lever, of brake-shoes mounted in successive relationship thereon adapted to rock about an axis lying transversely of the lever and movable on said lever in the direction of their length, the adjacent endsof the shoes co-operating one with another to cause them to rock in unison and diametrically disposed xed stops adapted to arrest endwise movement of the shoes.

5. In an expanding brake, the combination with a lever mounted to rock towards and away from a member to be braked, and means for rocking the lever, of a brake-shoe movably supported on said lever and movable bodily on said lever in the direction of its length, one end of the shoe moving away from its supporting lever and towards the member to be braked, the `other end of the shoe moving towards its supporting lever and away from the member to be braked, and means for limiting'the endwise movement of the shoe, including diametrically disposed abutments.

6. In an expanding brake ofthe character described, the combination with a lever mounted to rock towards and away from a member to be braked, and means for rocking the lever, of a rotatable fulcrum-piece mounted on said lever between its ends, a brake-shoe mounted to rock on said fulcrum-piece about an axis lying transversely of the direction of length of the lever,

lli() afg.

which shoe is adapted to move endwise on said fulcrum-piece in the direction of length of the lever, xed abutment means for limiting the endwise movement of the shoe in both directions, and a spring tending to hold the shoe seated on the fulcrum-piece, which spring extends between said shoe and said fulcrum-piece and constitutes a bearing member between these two parts.

7. In an expanding brake of the character described, the combination with a lever mounted to rock towards and away from a member to be braked, and means for rocking the lever, of fulcrum-pieces rotatable on said lever between its ends each about an axis lying transversely of the direction of'length of the lever, brake-shoes mounted in successive relationship to rock one on each ulcrum-piece about an axis lying transversely of the direction of length of the lever, which shoes are adapted each to move endwise on its fulcrum-piece in the direction'or" length of the lever, fixed stops between which said shoes are movable, which stops are arranged to limit the endwise movement of the shoes in both directions, and resilient means tending to seat each shoe on its allotted fulcrum-piece.

8. In an expanding brake of the character described, the combination with a lever mounted to rock towards and away from a memberv to be braked, and means for rocking the lever, of rollers constituting fulcrum-pieces journaled spaced apart on said lever between its ends with their axes of rotation lying transversely or" the direction of length of the lever, brake-shoes mounted in successive relationship to rock one on each roller about an axis parallel with said rollers, which shoes are adapted to move endwise each on its roller in the direction of length of the lever, the adjacent ends of which shoes so co-operate one withlanother as to cause them to rock in unison and to cause endwise movement of one of them to be imparted to another, xed stops between which said shoes are movable, which stops are arranged to limit the endwise movement of the shoes in` both directions, and a spring tending to seat each shoe on its allotted roller.

9. In an expanding brake of the character described, theA combination with a lever mounted to rock towards and away from a member to be braked, and means for rocking the lever, of rollers constituting fulcrum-pieces journaled spaced apart on said lever between its ends with their axes of rotation lying transversely of the direction of length of the lever, brake-shoes mounted in successive relationship to rock one on each roller about an axis parallel with the axes of rotation of said rollers, which shoes are adapted to move endwise each on its roller in the direction of length of the lever, the adjacent ends of which shoes so co-operate one with another as to cause them to rock in unison and to cause endwise movement of one of them to be imparted to another, fixed stops between which shoes are movable, which stops are arranged to limit the endwise movement of the shoes in both directions, a spring carried by said lever and extending between each shoe and its allotted roller, and means operatively connecting the ends of said spring with said shoes so as to cause the shoes to be seated by the spring on the rollers.

10. In brake mechanism for engaging a rotatable drum, a compound brake element having self-wrapping characteristics in the direction of the normal rotation of the drum composed of a plurality of articulated shoes and a xed anchor noemer engaging one of the shoes, said element being mounted on a common brake-applying member.

1l. In brake mechanism for engaging a rotatable drum, a self-energizing brake comprising articulated primary and secondary shoes both mounted upon a common applying means and oppositely disposed anchors adapted for co-operation with the shoes.

l2. In brake mechanism for engaging a rotatable drum, a self-energizing brake consisting of articulated primary and secondary shoes both mounted upon a common applying means and longitudinally slidable thereonand oppositely disposed xed abutments adaptable for co-operation with the shoes.

13. In brake mechanism for engaging a rotatable drum, a compound braking element comprising a primary shoe and a secondary-shoe jointed thereto, both shoes mounted upon a common applying means and one or the other of said shoes anchoring on one of two fixed abutments.

14. A brake comprising, a primary braking element adapted to anchor at one end thereof upon a fixed abutment and a servo element disconnectedly engaging said primary element and functioning to apply the latter, both of said .elements being mounted upon a brake-applying member with sliding movement thereover.

15. In brake mechanism for engaging a rotatable drum, a pair of brake shoes, at least one of said shoes having self-energizing characteristics in either direction of drum rotation and the remaining shoe functioning as a servo shoe for said aforementioned shoe, both of said shoes beingr mounted upon a common applying means and spaced abutments adapted for co-operation with the shoes.

16. A brake comprising, in combination, a rotatable drum, two pairs of juxtaposed shoes, each pair comprising a principal shoe and a servo shoe therefor each pair of shoes being mounted upon a common applying means and spaced abutments adapted for co-operation with the shoes.

17. A brake comprising a pair of shoes mounted on a common applying element, said shoes anchoring at one end of one shoe when the drum is turning in one direction and anchoring at one end of the other shoe when the drum is turning in the other direction.

18. A brake comprising, in combination, a rotatable drum, a xed abutment and a plurality of brake elements adapted to contact said drum and further characterized by said elements being mounted on a common support and anchoring on said abutment at an appreciable distance from said drum.

19. A brake comprising a plurality of self-energizing shoes slidably mounted upon a movable brake-applying element and anchoring upon a xed abutment, said shoes being so constructed and arranged as to make the self-energizing action cumulative.

20. A brake comprising oppositely disposed anchors each having parallel sides and a wedge shaped end portion.

21. A brake comprising a fixed support, a housing on the support, a pivot pin extending through the housing and levers fulcrumed on the pin within the housing.

22. A brake comprising a housing having parallel side Walls and a wedge shaped end portion, a pivot pin extending through the housing and levers fulcrumed on the pin within the housing.

23. A brake comprising a xed support, a housing onl the support, a cam positioned for lll() lli movement Within the housing and a lever engagm ing the cam.

2li. loralre comprising a housing having parI allel sides and a wedge shaped end port-ion, a shaft positioned for rotation in the housing, a cam on the shaft and a lever engaging the cam.

25. loralre comprising a backing plate, dia metrally disposed anchors positioned on the hacking plate each having parallel sides andA wedge shaped end portions, a pivot pin positioned on one of the anchors, a rotatable shaft positioned on the other anchor, a cam on the rotatable shaft and a lever fulcrumed on the hired shaft and engaging the cam.

26. A brake comprising a hacking plate, oppositely disposed housings arranged on the backing plate each having parallel side portions and a Wedge shaped end portion deiining an anchor, a pivot pin positioned in one of the housings, a rotatable shaft positioned in the other housing, a cam on the rotatable shaft and corresponding oppositely arranged levers fulcrumed on the iixed shaft and engaging the cam.

27. A brake comprising a plurality of articulated friction elements mounted on a common applying means and means intermediate the friction elements and the applying means for retaining the friction elements on the applying means.

28. A brake comprising a plurality of articulated friction elements positioned for move ment on a common applying means and a tension member for retaining the friction elements in engagement with the applying means.

29. A brake comprising acticulated primary and secondary shoes both mounted on a common applying means and means for yieldingly securing the primary and secondary shoes to the applying means providing for endvvise movement of the shoes.

30. A brake comprising articulated primary and secondary shoes, a common applying means for both shoes having thrust rollers engaging the shoes and a tension member connected between the shoes and the applyingv means adapted to retain the shoes in engagement with the thrust rollers.

31. A brake comprising articulated primary and secondary shoes, an applying lever common to both shoes, thrust rollers carried by the lever engaging the shoes, a leaf spring attached to the lever by a clip and clips on the shoes engaging the respective ends of the spring to retain the shoes in engagement with the thrust rollers.

32. A brake comprising channeled shoes, an applying means for the shoes positioned in the channels and means positioned longitudinally in the channels for yieldingly connectingthe shoes and the applying means. i

33. A braise comprising articulated primary and secondary shoes each having a channel in its inner periphery, an applying means positioned in the channels and means positioned longitudinally Within the channel for securing the shoes to the applying means.

3A. hralae comprising articulated primary and secondary shoes each having a channel in its inner periphery, an applying means positioned in the channels, thrust rollers positioned on the applyingl means engaging the shoes and means within the channel exihly connecting the shoes with the applying means to provide for movement of the shoes on the thrust rollers.

35. A brake comprising a channelled shoe., an applying means for the shoe positioned longitudinally in the channel of the shoe-and means also positioned longitudinally in the channel for yieldingly retracting the shoe.

36, A brake comprising a channelled shoe, an applying means for the shoe comprising a lever positioned longitudinally in the channel of the shoe, and means also positioned longitudinally in the channel for yieldingly retracting the shoe.

37. A brake having a plurality of channelled shoes shiftable to anchor at opposite ends, anchoring means adjacent the ends of the shoes, and means comprising an element common to two adjacent shoes and lying partially Within the channels of said adjacent shoes for forcing the shoes outwardly to applied position.

38. A brake having a channelled shoe, an operating lever in the channel of the shoe, and a retracting spring between the lever and said shoe.

39. A brake comprising a plurality of shoes each shiftable to anchor at opposite ends, anchoring means adjacent the ends of the shoes. and a curved lever fulcruined on a support and engaging two adjacent shoes intermediate their ends.

40. A brake comprising a support, a plurality of shiftable shoes. anchoring means therefor on said support, and actuating means comprising a cam on said support and an arcuate lever pivoted at a pointsubstantially diametrically opposite said cam, said lever engaging two adjacent shoes at points intermediate of their ends.

,41. A brake comprising a plurality of shiftable shoes, anchoring means therefor, and actuating means comprising a pivoted curved element engaging two adjacent shoes intermediate of their ends..

ALBERT HENRY GODFREY GIRLING. 

